WILLIAMS, G. A., BOLEN, M. C., & DOERHOFF Ray B. (1973). Challenges to science physical science. Wbster Division, McGraw-Hill Book Company.
Cita Chicago (17th ed.)WILLIAMS, George A., Max C. BOLEN, i DOERHOFF Ray B. Challenges to Science Physical Science. New York: Wbster Division, McGraw-Hill Book Company, 1973.
Cita MLA (9th ed.)WILLIAMS, George A., et al. Challenges to Science Physical Science. Wbster Division, McGraw-Hill Book Company, 1973.
Atenció: Aquestes cites poden no estar 100% correctes.